Our research will include studying the tissue distribution of murine Ia gene expression by analyzing the presence of Ia-specific messenger RNAs in tissues and cell lines. We will use DNA probes derived from four cloned Ia genes, A-alpha, A-beta, E-alpha, and E-beta, in combination with three sensitive RNA assays, dot blots, Northern blots, and S[unreadable]1[unreadable] nuclease mapping, to critically evaluate the tissues capable of Ia gene expression as well as their capacity for Ia gene induction. S[unreadable]1[unreadable] nuclease mapping will aIso be used to determine if there is any alternative processing of Ia mRNA. Our investigstion will determine the ability of nonbone marrow-derived cells to express Ia genes by producing radiation chimeras. The characteristics of Ia gene induction in both tissues and cell lines including macrophages, dendritic cells, and T cells will be evaluated using known inducing agents including gamma interferon. We intend to critically test a recent hypothesis that Ia antigens are induced in grafted tissue on cells other than "passenger leukocytes" as a consequence of the allograft reaction. Finally, we will study the mechanism of Ia gene induction by transfecting cloned Ia genes into different cell types and selecting for inducible expression. (MB)